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	$224.28	9.486%	$245.5552	$245.56	$245.55	$245.60
Purchase #2	$37.74	7.808%	$40.6867	$40.69	$40.70	$40.70
Purchase #3	$92.54	6.231%	$98.3062	$98.31	$98.30	$98.30
Purchase #4	$82.35	10.457%	$90.9613	$90.96	$90.95	$91.00
Purchase #5	$69.76	3.232%	$72.0146	$72.01	$72.00	$72.00
Purchase #6	$116.36	13.562%	$132.1407	$132.14	$132.15	$132.10
Purchase #7	$250.88	7.155%	$268.8305	$268.83	$268.85	$268.80
7 purchase totals =	$873.91		$948.4952	$948.50	$948.50	$948.50