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	$129.69	11.310%	$144.3579	$144.36	$144.35	$144.40
Purchase #2	$182.74	7.661%	$196.7397	$196.74	$196.75	$196.70
Purchase #3	$92.44	7.739%	$99.5939	$99.59	$99.60	$99.60
Purchase #4	$229.70	12.729%	$258.9385	$258.94	$258.95	$258.90
Purchase #5	$213.74	8.710%	$232.3568	$232.36	$232.35	$232.40
Purchase #6	$61.91	10.629%	$68.4904	$68.49	$68.50	$68.50
Purchase #7	$111.69	13.762%	$127.0608	$127.06	$127.05	$127.10
7 purchase totals =	$1,021.91		$1,127.5380	$1,127.54	$1,127.55	$1,127.60