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	$39.84	11.435%	$44.3957	$44.40	$44.40	$44.40
Purchase #2	$240.89	4.307%	$251.2651	$251.27	$251.25	$251.30
Purchase #3	$74.54	5.583%	$78.7016	$78.70	$78.70	$78.70
Purchase #4	$91.27	5.463%	$96.2561	$96.26	$96.25	$96.30
Purchase #5	$188.52	12.343%	$211.789	$211.79	$211.80	$211.80
Purchase #6	$213.54	13.481%	$242.3273	$242.33	$242.35	$242.30
Purchase #7	$74.86	13.588%	$85.032	$85.03	$85.05	$85.00
7 purchase totals =	$923.46		$1,009.7668	$1,009.78	$1,009.80	$1,009.80