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	$79.82	4.215%	$83.1844	$83.18	$83.20	$83.20
Purchase #2	$8.78	6.735%	$9.3713	$9.37	$9.35	$9.40
Purchase #3	$242.30	8.563%	$263.0481	$263.05	$263.05	$263.00
Purchase #4	$41.54	4.454%	$43.3902	$43.39	$43.40	$43.40
Purchase #5	$63.49	13.235%	$71.8929	$71.89	$71.90	$71.90
Purchase #6	$250.57	13.289%	$283.8682	$283.87	$283.85	$283.90
Purchase #7	$243.55	8.625%	$264.5562	$264.56	$264.55	$264.60
7 purchase totals =	$930.05		$1,019.3113	$1,019.31	$1,019.30	$1,019.40