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	$99.33	13.108%	$112.3502	$112.35	$112.35	$112.40
Purchase #2	$73.36	6.431%	$78.0778	$78.08	$78.10	$78.10
Purchase #3	$88.39	3.774%	$91.7258	$91.73	$91.75	$91.70
Purchase #4	$142.70	5.317%	$150.2874	$150.29	$150.30	$150.30
Purchase #5	$23.98	10.227%	$26.4324	$26.43	$26.45	$26.40
Purchase #6	$220.25	13.145%	$249.2019	$249.20	$249.20	$249.20
Purchase #7	$53.59	11.291%	$59.6408	$59.64	$59.65	$59.60
7 purchase totals =	$701.60		$767.7163	$767.72	$767.80	$767.70