Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$167.40	12.684%	$188.633	$188.63	$188.65	$188.60
Purchase #2	$155.28	6.432%	$165.2676	$165.27	$165.25	$165.30
Purchase #3	$184.62	13.634%	$209.7911	$209.79	$209.80	$209.80
Purchase #4	$240.62	13.715%	$273.621	$273.62	$273.60	$273.60
Purchase #5	$152.95	7.456%	$164.354	$164.35	$164.35	$164.40
Purchase #6	$145.69	12.794%	$164.3296	$164.33	$164.35	$164.30
Purchase #7	$130.27	13.850%	$148.3124	$148.31	$148.30	$148.30
7 purchase totals =	$1,176.83		$1,314.3087	$1,314.30	$1,314.30	$1,314.30