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	$165.38	4.462%	$172.7593	$172.76	$172.75	$172.80
Purchase #2	$83.33	6.751%	$88.9556	$88.96	$88.95	$89.00
Purchase #3	$157.56	13.143%	$178.2681	$178.27	$178.25	$178.30
Purchase #4	$134.64	12.644%	$151.6639	$151.66	$151.65	$151.70
Purchase #5	$241.31	11.297%	$268.5708	$268.57	$268.55	$268.60
Purchase #6	$47.94	6.295%	$50.9578	$50.96	$50.95	$51.00
Purchase #7	$51.53	10.737%	$57.0628	$57.06	$57.05	$57.10
7 purchase totals =	$881.69		$968.2383	$968.24	$968.15	$968.50