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	$72.60	13.734%	$82.5709	$82.57	$82.55	$82.60
Purchase #2	$89.96	4.676%	$94.1665	$94.17	$94.15	$94.20
Purchase #3	$73.91	8.668%	$80.3165	$80.32	$80.30	$80.30
Purchase #4	$175.48	5.140%	$184.4997	$184.50	$184.50	$184.50
Purchase #5	$202.41	13.261%	$229.2516	$229.25	$229.25	$229.30
Purchase #6	$89.47	7.280%	$95.9834	$95.98	$96.00	$96.00
Purchase #7	$220.47	13.340%	$249.8807	$249.88	$249.90	$249.90
7 purchase totals =	$924.30		$1,016.6693	$1,016.67	$1,016.65	$1,016.80