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	$155.37	6.236%	$165.0589	$165.06	$165.05	$165.10
Purchase #2	$53.62	9.795%	$58.8721	$58.87	$58.85	$58.90
Purchase #3	$100.53	8.603%	$109.1786	$109.18	$109.20	$109.20
Purchase #4	$152.76	10.393%	$168.6363	$168.64	$168.65	$168.60
Purchase #5	$247.65	7.676%	$266.6596	$266.66	$266.65	$266.70
Purchase #6	$79.91	9.542%	$87.535	$87.54	$87.55	$87.50
Purchase #7	$233.31	9.357%	$255.1408	$255.14	$255.15	$255.10
7 purchase totals =	$1,023.15		$1,111.0813	$1,111.09	$1,111.10	$1,111.10