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	$194.44	6.203%	$206.5011	$206.50	$206.50	$206.50
Purchase #2	$223.34	11.607%	$249.2631	$249.26	$249.25	$249.30
Purchase #3	$107.48	7.279%	$115.3035	$115.30	$115.30	$115.30
Purchase #4	$134.52	9.578%	$147.4043	$147.40	$147.40	$147.40
Purchase #5	$152.89	13.131%	$172.966	$172.97	$172.95	$173.00
Purchase #6	$205.55	6.288%	$218.475	$218.48	$218.50	$218.50
Purchase #7	$29.29	11.266%	$32.5898	$32.59	$32.60	$32.60
7 purchase totals =	$1,047.51		$1,142.5028	$1,142.50	$1,142.50	$1,142.60