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	$149.84	4.717%	$156.908	$156.91	$156.90	$156.90
Purchase #2	$84.80	8.817%	$92.2768	$92.28	$92.30	$92.30
Purchase #3	$114.73	11.154%	$127.527	$127.53	$127.55	$127.50
Purchase #4	$22.62	7.271%	$24.2647	$24.26	$24.25	$24.30
Purchase #5	$62.98	7.754%	$67.8635	$67.86	$67.85	$67.90
Purchase #6	$33.85	12.558%	$38.1009	$38.10	$38.10	$38.10
Purchase #7	$89.33	13.663%	$101.5352	$101.54	$101.55	$101.50
7 purchase totals =	$558.15		$608.4761	$608.48	$608.50	$608.50