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	$203.55	3.814%	$211.3134	$211.31	$211.30	$211.30
Purchase #2	$120.31	13.809%	$136.9236	$136.92	$136.90	$136.90
Purchase #3	$30.72	5.183%	$32.3122	$32.31	$32.30	$32.30
Purchase #4	$80.86	3.804%	$83.9359	$83.94	$83.95	$83.90
Purchase #5	$243.74	4.306%	$254.2354	$254.24	$254.25	$254.20
Purchase #6	$164.39	4.481%	$171.7563	$171.76	$171.75	$171.80
Purchase #7	$174.99	13.198%	$198.0852	$198.09	$198.10	$198.10
7 purchase totals =	$1,018.56		$1,088.5620	$1,088.57	$1,088.55	$1,088.50