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	$169.98	10.493%	$187.816	$187.82	$187.80	$187.80
Purchase #2	$29.30	13.742%	$33.3264	$33.33	$33.35	$33.30
Purchase #3	$168.40	4.478%	$175.941	$175.94	$175.95	$175.90
Purchase #4	$180.78	3.234%	$186.6264	$186.63	$186.65	$186.60
Purchase #5	$194.26	3.351%	$200.7697	$200.77	$200.75	$200.80
Purchase #6	$43.73	8.839%	$47.5953	$47.60	$47.60	$47.60
Purchase #7	$207.86	10.286%	$229.2405	$229.24	$229.25	$229.20
7 purchase totals =	$994.31		$1,061.3153	$1,061.33	$1,061.35	$1,061.20