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	$141.69	4.277%	$147.7501	$147.75	$147.75	$147.80
Purchase #2	$19.25	9.629%	$21.1036	$21.10	$21.10	$21.10
Purchase #3	$100.36	4.738%	$105.1151	$105.12	$105.10	$105.10
Purchase #4	$224.42	7.114%	$240.3852	$240.39	$240.40	$240.40
Purchase #5	$95.33	3.643%	$98.8029	$98.80	$98.80	$98.80
Purchase #6	$210.34	6.245%	$223.4757	$223.48	$223.50	$223.50
Purchase #7	$195.27	9.867%	$214.5373	$214.54	$214.55	$214.50
7 purchase totals =	$986.66		$1,051.1699	$1,051.18	$1,051.20	$1,051.20