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	$104.41	8.585%	$113.3736	$113.37	$113.35	$113.40
Purchase #2	$237.75	13.192%	$269.114	$269.11	$269.10	$269.10
Purchase #3	$60.49	11.269%	$67.3066	$67.31	$67.30	$67.30
Purchase #4	$234.70	5.412%	$247.402	$247.40	$247.40	$247.40
Purchase #5	$189.59	3.558%	$196.3356	$196.34	$196.35	$196.30
Purchase #6	$98.55	13.369%	$111.7251	$111.73	$111.75	$111.70
Purchase #7	$164.90	5.739%	$174.3636	$174.36	$174.35	$174.40
7 purchase totals =	$1,090.39		$1,179.6205	$1,179.62	$1,179.60	$1,179.60