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	$97.56	4.572%	$102.0204	$102.02	$102.00	$102.00
Purchase #2	$240.48	4.568%	$251.4651	$251.47	$251.45	$251.50
Purchase #3	$145.72	3.591%	$150.9528	$150.95	$150.95	$151.00
Purchase #4	$5.39	8.405%	$5.843	$5.84	$5.85	$5.80
Purchase #5	$82.63	8.404%	$89.5742	$89.57	$89.55	$89.60
Purchase #6	$31.63	12.262%	$35.5085	$35.51	$35.50	$35.50
Purchase #7	$91.31	3.811%	$94.7898	$94.79	$94.80	$94.80
7 purchase totals =	$694.72		$730.1538	$730.15	$730.10	$730.20