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	$148.33	3.105%	$152.9356	$152.94	$152.95	$152.90
Purchase #2	$148.45	6.555%	$158.1809	$158.18	$158.20	$158.20
Purchase #3	$96.47	13.328%	$109.3275	$109.33	$109.35	$109.30
Purchase #4	$89.87	3.552%	$93.0622	$93.06	$93.05	$93.10
Purchase #5	$26.86	12.212%	$30.1401	$30.14	$30.15	$30.10
Purchase #6	$210.45	13.243%	$238.3199	$238.32	$238.30	$238.30
Purchase #7	$64.76	12.303%	$72.7274	$72.73	$72.75	$72.70
7 purchase totals =	$785.19		$854.6936	$854.70	$854.75	$854.60