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	$127.66	3.468%	$132.0872	$132.09	$132.10	$132.10
Purchase #2	$53.55	3.579%	$55.4666	$55.47	$55.45	$55.50
Purchase #3	$187.36	4.159%	$195.1523	$195.15	$195.15	$195.20
Purchase #4	$218.88	10.700%	$242.3002	$242.30	$242.30	$242.30
Purchase #5	$154.31	9.710%	$169.2935	$169.29	$169.30	$169.30
Purchase #6	$236.90	13.356%	$268.5404	$268.54	$268.55	$268.50
Purchase #7	$117.30	8.491%	$127.2599	$127.26	$127.25	$127.30
7 purchase totals =	$1,095.96		$1,190.1001	$1,190.10	$1,190.10	$1,190.20