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	$241.40	3.611%	$250.117	$250.12	$250.10	$250.10
Purchase #2	$35.38	6.663%	$37.7374	$37.74	$37.75	$37.70
Purchase #3	$11.90	10.781%	$13.1829	$13.18	$13.20	$13.20
Purchase #4	$180.91	13.482%	$205.3003	$205.30	$205.30	$205.30
Purchase #5	$162.45	3.168%	$167.5964	$167.60	$167.60	$167.60
Purchase #6	$188.25	4.177%	$196.1132	$196.11	$196.10	$196.10
Purchase #7	$217.56	7.427%	$233.7182	$233.72	$233.70	$233.70
7 purchase totals =	$1,037.85		$1,103.7654	$1,103.77	$1,103.75	$1,103.70