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	$156.69	6.655%	$167.1177	$167.12	$167.10	$167.10
Purchase #2	$102.59	7.803%	$110.5951	$110.60	$110.60	$110.60
Purchase #3	$62.66	13.825%	$71.3227	$71.32	$71.30	$71.30
Purchase #4	$188.66	4.153%	$196.495	$196.50	$196.50	$196.50
Purchase #5	$65.28	3.774%	$67.7437	$67.74	$67.75	$67.70
Purchase #6	$91.26	9.571%	$99.9945	$99.99	$100.00	$100.00
Purchase #7	$29.56	9.592%	$32.3954	$32.40	$32.40	$32.40
7 purchase totals =	$696.70		$745.6641	$745.67	$745.65	$745.60