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	$181.39	3.524%	$187.7822	$187.78	$187.80	$187.80
Purchase #2	$37.28	4.453%	$38.9401	$38.94	$38.95	$38.90
Purchase #3	$142.94	9.764%	$156.8967	$156.90	$156.90	$156.90
Purchase #4	$182.93	3.453%	$189.2466	$189.25	$189.25	$189.20
Purchase #5	$49.71	5.712%	$52.5494	$52.55	$52.55	$52.50
Purchase #6	$107.77	3.628%	$111.6799	$111.68	$111.70	$111.70
Purchase #7	$53.26	3.468%	$55.1071	$55.11	$55.10	$55.10
7 purchase totals =	$755.28		$792.2020	$792.21	$792.25	$792.10