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	$91.35	8.446%	$99.0654	$99.07	$99.05	$99.10
Purchase #2	$192.87	8.563%	$209.3855	$209.39	$209.40	$209.40
Purchase #3	$155.55	10.286%	$171.5499	$171.55	$171.55	$171.50
Purchase #4	$170.57	5.845%	$180.5398	$180.54	$180.55	$180.50
Purchase #5	$128.37	9.318%	$140.3315	$140.33	$140.35	$140.30
Purchase #6	$171.89	5.702%	$181.6912	$181.69	$181.70	$181.70
Purchase #7	$25.89	6.480%	$27.5677	$27.57	$27.55	$27.60
7 purchase totals =	$936.49		$1,010.1310	$1,010.14	$1,010.15	$1,010.10