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	$101.30	4.129%	$105.4827	$105.48	$105.50	$105.50
Purchase #2	$205.59	8.729%	$223.536	$223.54	$223.55	$223.50
Purchase #3	$135.58	3.406%	$140.1979	$140.20	$140.20	$140.20
Purchase #4	$170.61	5.275%	$179.6097	$179.61	$179.60	$179.60
Purchase #5	$215.39	13.445%	$244.3492	$244.35	$244.35	$244.30
Purchase #6	$168.26	13.659%	$191.2426	$191.24	$191.25	$191.20
Purchase #7	$27.33	11.376%	$30.4391	$30.44	$30.45	$30.40
7 purchase totals =	$1,024.06		$1,114.8572	$1,114.86	$1,114.90	$1,114.70