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	$41.98	12.285%	$47.1372	$47.14	$47.15	$47.10
Purchase #2	$57.48	12.288%	$64.5431	$64.54	$64.55	$64.50
Purchase #3	$65.98	7.693%	$71.0558	$71.06	$71.05	$71.10
Purchase #4	$43.75	9.117%	$47.7387	$47.74	$47.75	$47.70
Purchase #5	$134.98	9.343%	$147.5912	$147.59	$147.60	$147.60
Purchase #6	$131.74	8.140%	$142.4636	$142.46	$142.45	$142.50
Purchase #7	$90.42	3.849%	$93.9003	$93.90	$93.90	$93.90
7 purchase totals =	$566.33		$614.4299	$614.43	$614.45	$614.40