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	$190.42	10.861%	$211.1015	$211.10	$211.10	$211.10
Purchase #2	$121.96	4.378%	$127.2994	$127.30	$127.30	$127.30
Purchase #3	$250.77	7.451%	$269.4549	$269.45	$269.45	$269.50
Purchase #4	$139.53	9.835%	$153.2528	$153.25	$153.25	$153.30
Purchase #5	$38.28	8.301%	$41.4576	$41.46	$41.45	$41.50
Purchase #6	$167.72	13.471%	$190.3136	$190.31	$190.30	$190.30
Purchase #7	$179.73	10.224%	$198.1056	$198.11	$198.10	$198.10
7 purchase totals =	$1,088.41		$1,190.9854	$1,190.98	$1,190.95	$1,191.10