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	$109.85	13.399%	$124.5688	$124.57	$124.55	$124.60
Purchase #2	$80.32	5.533%	$84.7641	$84.76	$84.75	$84.80
Purchase #3	$141.53	13.872%	$161.163	$161.16	$161.15	$161.20
Purchase #4	$212.80	5.119%	$223.6932	$223.69	$223.70	$223.70
Purchase #5	$131.31	6.535%	$139.8911	$139.89	$139.90	$139.90
Purchase #6	$81.44	5.452%	$85.8801	$85.88	$85.90	$85.90
Purchase #7	$165.51	13.758%	$188.2809	$188.28	$188.30	$188.30
7 purchase totals =	$922.76		$1,008.2412	$1,008.23	$1,008.25	$1,008.40