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	$95.32	3.297%	$98.4627	$98.46	$98.45	$98.50
Purchase #2	$49.93	10.146%	$54.9959	$55.00	$55.00	$55.00
Purchase #3	$33.82	9.542%	$37.0471	$37.05	$37.05	$37.00
Purchase #4	$204.62	7.482%	$219.9297	$219.93	$219.95	$219.90
Purchase #5	$210.78	11.521%	$235.064	$235.06	$235.05	$235.10
Purchase #6	$37.54	9.642%	$41.1596	$41.16	$41.15	$41.20
Purchase #7	$105.40	6.872%	$112.6431	$112.64	$112.65	$112.60
7 purchase totals =	$737.41		$799.3021	$799.30	$799.30	$799.30