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	$37.64	7.521%	$40.4709	$40.47	$40.45	$40.50
Purchase #2	$249.91	5.856%	$264.5447	$264.54	$264.55	$264.50
Purchase #3	$196.38	7.654%	$211.4109	$211.41	$211.40	$211.40
Purchase #4	$145.96	13.331%	$165.4179	$165.42	$165.40	$165.40
Purchase #5	$187.46	10.405%	$206.9652	$206.97	$206.95	$207.00
Purchase #6	$216.84	12.420%	$243.7715	$243.77	$243.75	$243.80
Purchase #7	$209.89	11.418%	$233.8552	$233.86	$233.85	$233.90
7 purchase totals =	$1,244.08		$1,366.4363	$1,366.44	$1,366.35	$1,366.50