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	$210.33	5.218%	$221.305	$221.31	$221.30	$221.30
Purchase #2	$94.90	4.588%	$99.254	$99.25	$99.25	$99.30
Purchase #3	$250.54	11.104%	$278.36	$278.36	$278.35	$278.40
Purchase #4	$236.93	7.570%	$254.8656	$254.87	$254.85	$254.90
Purchase #5	$170.56	9.527%	$186.8093	$186.81	$186.80	$186.80
Purchase #6	$152.30	8.462%	$165.1876	$165.19	$165.20	$165.20
Purchase #7	$179.35	3.761%	$186.0954	$186.10	$186.10	$186.10
7 purchase totals =	$1,294.91		$1,391.8769	$1,391.89	$1,391.85	$1,392.00