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	$215.86	10.409%	$238.3289	$238.33	$238.35	$238.30
Purchase #2	$83.52	12.375%	$93.8556	$93.86	$93.85	$93.90
Purchase #3	$179.76	5.795%	$190.1771	$190.18	$190.20	$190.20
Purchase #4	$29.48	10.232%	$32.4964	$32.50	$32.50	$32.50
Purchase #5	$71.91	12.294%	$80.7506	$80.75	$80.75	$80.80
Purchase #6	$136.71	10.599%	$151.1999	$151.20	$151.20	$151.20
Purchase #7	$142.27	3.364%	$147.056	$147.06	$147.05	$147.10
7 purchase totals =	$859.51		$933.8645	$933.88	$933.90	$934.00