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	$69.52	3.432%	$71.9059	$71.91	$71.90	$71.90
Purchase #2	$223.39	9.828%	$245.3448	$245.34	$245.35	$245.30
Purchase #3	$29.32	6.504%	$31.227	$31.23	$31.25	$31.20
Purchase #4	$182.31	3.397%	$188.5031	$188.50	$188.50	$188.50
Purchase #5	$223.74	9.471%	$244.9304	$244.93	$244.95	$244.90
Purchase #6	$86.58	3.242%	$89.3869	$89.39	$89.40	$89.40
Purchase #7	$162.35	11.489%	$181.0024	$181.00	$181.00	$181.00
7 purchase totals =	$977.21		$1,052.3005	$1,052.30	$1,052.35	$1,052.20