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	$117.41	11.322%	$130.7032	$130.70	$130.70	$130.70
Purchase #2	$12.76	11.663%	$14.2482	$14.25	$14.25	$14.20
Purchase #3	$214.74	5.394%	$226.3231	$226.32	$226.30	$226.30
Purchase #4	$183.71	9.321%	$200.8336	$200.83	$200.85	$200.80
Purchase #5	$83.61	8.516%	$90.7302	$90.73	$90.75	$90.70
Purchase #6	$185.83	5.524%	$196.0952	$196.10	$196.10	$196.10
Purchase #7	$39.59	11.825%	$44.2715	$44.27	$44.25	$44.30
7 purchase totals =	$837.65		$903.2050	$903.20	$903.20	$903.10