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	$154.64	12.590%	$174.1092	$174.11	$174.10	$174.10
Purchase #2	$89.45	7.645%	$96.2885	$96.29	$96.30	$96.30
Purchase #3	$25.31	7.833%	$27.2925	$27.29	$27.30	$27.30
Purchase #4	$67.96	6.315%	$72.2517	$72.25	$72.25	$72.30
Purchase #5	$61.97	8.816%	$67.4333	$67.43	$67.45	$67.40
Purchase #6	$43.39	11.190%	$48.2453	$48.25	$48.25	$48.20
Purchase #7	$46.44	6.439%	$49.4303	$49.43	$49.45	$49.40
7 purchase totals =	$489.16		$535.0508	$535.05	$535.10	$535.00