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	$97.75	3.564%	$101.2338	$101.23	$101.25	$101.20
Purchase #2	$95.71	4.197%	$99.7269	$99.73	$99.75	$99.70
Purchase #3	$250.78	7.207%	$268.8537	$268.85	$268.85	$268.90
Purchase #4	$100.40	3.171%	$103.5837	$103.58	$103.60	$103.60
Purchase #5	$201.76	13.726%	$229.4536	$229.45	$229.45	$229.50
Purchase #6	$242.33	11.833%	$271.0049	$271.00	$271.00	$271.00
Purchase #7	$49.45	8.110%	$53.4604	$53.46	$53.45	$53.50
7 purchase totals =	$1,038.18		$1,127.3170	$1,127.30	$1,127.35	$1,127.40