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	$218.25	3.705%	$226.3362	$226.34	$226.35	$226.30
Purchase #2	$147.55	13.105%	$166.8864	$166.89	$166.90	$166.90
Purchase #3	$48.77	3.308%	$50.3833	$50.38	$50.40	$50.40
Purchase #4	$186.76	11.328%	$207.9162	$207.92	$207.90	$207.90
Purchase #5	$44.67	3.109%	$46.0588	$46.06	$46.05	$46.10
Purchase #6	$233.72	4.359%	$243.9079	$243.91	$243.90	$243.90
Purchase #7	$96.47	3.545%	$99.8899	$99.89	$99.90	$99.90
7 purchase totals =	$976.19		$1,041.3787	$1,041.39	$1,041.40	$1,041.40