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	$89.26	9.431%	$97.6781	$97.68	$97.70	$97.70
Purchase #2	$18.69	11.450%	$20.83	$20.83	$20.85	$20.80
Purchase #3	$43.72	13.552%	$49.6449	$49.64	$49.65	$49.60
Purchase #4	$143.59	13.442%	$162.8914	$162.89	$162.90	$162.90
Purchase #5	$142.71	12.331%	$160.3076	$160.31	$160.30	$160.30
Purchase #6	$17.76	3.241%	$18.3356	$18.34	$18.35	$18.30
Purchase #7	$82.73	8.637%	$89.8754	$89.88	$89.90	$89.90
7 purchase totals =	$538.46		$599.5630	$599.57	$599.65	$599.50