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	$218.96	10.112%	$241.1012	$241.10	$241.10	$241.10
Purchase #2	$156.38	11.133%	$173.7898	$173.79	$173.80	$173.80
Purchase #3	$81.76	11.171%	$90.8934	$90.89	$90.90	$90.90
Purchase #4	$238.33	4.263%	$248.49	$248.49	$248.50	$248.50
Purchase #5	$139.74	6.135%	$148.313	$148.31	$148.30	$148.30
Purchase #6	$42.97	11.585%	$47.9481	$47.95	$47.95	$47.90
Purchase #7	$114.69	11.311%	$127.6626	$127.66	$127.65	$127.70
7 purchase totals =	$992.83		$1,078.1981	$1,078.19	$1,078.20	$1,078.20