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	$207.42	9.590%	$227.3116	$227.31	$227.30	$227.30
Purchase #2	$238.89	12.321%	$268.3236	$268.32	$268.30	$268.30
Purchase #3	$80.48	6.746%	$85.9092	$85.91	$85.90	$85.90
Purchase #4	$194.34	9.271%	$212.3573	$212.36	$212.35	$212.40
Purchase #5	$61.88	13.642%	$70.3217	$70.32	$70.30	$70.30
Purchase #6	$25.79	7.612%	$27.7531	$27.75	$27.75	$27.80
Purchase #7	$75.66	13.192%	$85.6411	$85.64	$85.65	$85.60
7 purchase totals =	$884.46		$977.6176	$977.61	$977.55	$977.60