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	$211.46	10.641%	$233.9615	$233.96	$233.95	$234.00
Purchase #2	$30.77	10.129%	$33.8867	$33.89	$33.90	$33.90
Purchase #3	$170.53	6.454%	$181.536	$181.54	$181.55	$181.50
Purchase #4	$159.47	9.412%	$174.4793	$174.48	$174.50	$174.50
Purchase #5	$17.67	7.846%	$19.0564	$19.06	$19.05	$19.10
Purchase #6	$87.59	13.131%	$99.0914	$99.09	$99.10	$99.10
Purchase #7	$209.38	13.322%	$237.2736	$237.27	$237.25	$237.30
7 purchase totals =	$886.87		$979.2849	$979.29	$979.30	$979.40