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	$201.77	10.283%	$222.518	$222.52	$222.50	$222.50
Purchase #2	$227.89	7.595%	$245.1982	$245.20	$245.20	$245.20
Purchase #3	$79.89	4.447%	$83.4427	$83.44	$83.45	$83.40
Purchase #4	$86.68	10.803%	$96.044	$96.04	$96.05	$96.00
Purchase #5	$204.37	9.271%	$223.3171	$223.32	$223.30	$223.30
Purchase #6	$77.43	13.869%	$88.1688	$88.17	$88.15	$88.20
Purchase #7	$166.31	13.245%	$188.3378	$188.34	$188.35	$188.30
7 purchase totals =	$1,044.34		$1,147.0266	$1,147.03	$1,147.00	$1,146.90