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	$226.26	4.790%	$237.0979	$237.10	$237.10	$237.10
Purchase #2	$75.40	10.500%	$83.317	$83.32	$83.30	$83.30
Purchase #3	$24.64	11.424%	$27.4549	$27.45	$27.45	$27.50
Purchase #4	$70.98	4.104%	$73.893	$73.89	$73.90	$73.90
Purchase #5	$208.94	10.700%	$231.2966	$231.30	$231.30	$231.30
Purchase #6	$110.52	12.267%	$124.0775	$124.08	$124.10	$124.10
Purchase #7	$210.56	6.790%	$224.857	$224.86	$224.85	$224.90
7 purchase totals =	$927.30		$1,001.9939	$1,002.00	$1,002.00	$1,002.10