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	$234.95	6.117%	$249.3219	$249.32	$249.30	$249.30
Purchase #2	$14.84	3.669%	$15.3845	$15.38	$15.40	$15.40
Purchase #3	$243.40	8.643%	$264.4371	$264.44	$264.45	$264.40
Purchase #4	$78.64	8.478%	$85.3071	$85.31	$85.30	$85.30
Purchase #5	$156.64	6.798%	$167.2884	$167.29	$167.30	$167.30
Purchase #6	$183.88	9.188%	$200.7749	$200.77	$200.75	$200.80
Purchase #7	$201.62	10.543%	$222.8768	$222.88	$222.90	$222.90
7 purchase totals =	$1,113.97		$1,205.3907	$1,205.39	$1,205.40	$1,205.40