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	$133.86	11.307%	$148.9956	$149.00	$149.00	$149.00
Purchase #2	$57.42	4.401%	$59.9471	$59.95	$59.95	$59.90
Purchase #3	$131.44	3.780%	$136.4084	$136.41	$136.40	$136.40
Purchase #4	$196.44	12.865%	$221.712	$221.71	$221.70	$221.70
Purchase #5	$190.76	12.342%	$214.3036	$214.30	$214.30	$214.30
Purchase #6	$7.40	4.584%	$7.7392	$7.74	$7.75	$7.70
Purchase #7	$209.95	6.104%	$222.7653	$222.77	$222.75	$222.80
7 purchase totals =	$927.27		$1,011.8712	$1,011.88	$1,011.85	$1,011.80