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	$227.94	7.144%	$244.224	$244.22	$244.20	$244.20
Purchase #2	$51.59	3.404%	$53.3461	$53.35	$53.35	$53.30
Purchase #3	$117.43	13.529%	$133.3171	$133.32	$133.30	$133.30
Purchase #4	$93.55	9.865%	$102.7787	$102.78	$102.80	$102.80
Purchase #5	$237.41	9.424%	$259.7835	$259.78	$259.80	$259.80
Purchase #6	$172.91	13.544%	$196.3289	$196.33	$196.35	$196.30
Purchase #7	$145.97	13.655%	$165.9022	$165.90	$165.90	$165.90
7 purchase totals =	$1,046.80		$1,155.6805	$1,155.68	$1,155.70	$1,155.60