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	$168.49	9.634%	$184.7223	$184.72	$184.70	$184.70
Purchase #2	$105.75	7.385%	$113.5596	$113.56	$113.55	$113.60
Purchase #3	$156.95	9.225%	$171.4286	$171.43	$171.45	$171.40
Purchase #4	$24.29	12.841%	$27.4091	$27.41	$27.40	$27.40
Purchase #5	$147.44	5.300%	$155.2543	$155.25	$155.25	$155.30
Purchase #6	$239.81	4.364%	$250.2753	$250.28	$250.30	$250.30
Purchase #7	$196.81	6.655%	$209.9077	$209.91	$209.90	$209.90
7 purchase totals =	$1,039.54		$1,112.5569	$1,112.56	$1,112.55	$1,112.60