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	$219.68	6.109%	$233.1003	$233.10	$233.10	$233.10
Purchase #2	$63.72	3.190%	$65.7527	$65.75	$65.75	$65.80
Purchase #3	$211.94	12.634%	$238.7165	$238.72	$238.70	$238.70
Purchase #4	$48.79	6.712%	$52.0648	$52.06	$52.05	$52.10
Purchase #5	$130.54	8.607%	$141.7756	$141.78	$141.80	$141.80
Purchase #6	$96.47	13.730%	$109.7153	$109.72	$109.70	$109.70
Purchase #7	$77.32	8.114%	$83.5937	$83.59	$83.60	$83.60
7 purchase totals =	$848.46		$924.7189	$924.72	$924.70	$924.80