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	$209.88	11.383%	$233.7706	$233.77	$233.75	$233.80
Purchase #2	$90.50	6.160%	$96.0748	$96.07	$96.05	$96.10
Purchase #3	$208.59	9.456%	$228.3143	$228.31	$228.30	$228.30
Purchase #4	$121.87	5.751%	$128.8787	$128.88	$128.90	$128.90
Purchase #5	$184.91	3.292%	$190.9972	$191.00	$191.00	$191.00
Purchase #6	$43.32	10.433%	$47.8396	$47.84	$47.85	$47.80
Purchase #7	$89.32	9.735%	$98.0153	$98.02	$98.00	$98.00
7 purchase totals =	$948.39		$1,023.8905	$1,023.89	$1,023.85	$1,023.90