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	$54.73	7.401%	$58.7806	$58.78	$58.80	$58.80
Purchase #2	$90.98	10.487%	$100.5211	$100.52	$100.50	$100.50
Purchase #3	$202.94	9.421%	$222.059	$222.06	$222.05	$222.10
Purchase #4	$234.72	3.607%	$243.1864	$243.19	$243.20	$243.20
Purchase #5	$136.80	7.500%	$147.06	$147.06	$147.05	$147.10
Purchase #6	$195.27	11.803%	$218.3177	$218.32	$218.30	$218.30
Purchase #7	$154.86	13.364%	$175.5555	$175.56	$175.55	$175.60
7 purchase totals =	$1,070.30		$1,165.4803	$1,165.49	$1,165.45	$1,165.60