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	$73.41	3.786%	$76.1893	$76.19	$76.20	$76.20
Purchase #2	$187.35	4.384%	$195.5634	$195.56	$195.55	$195.60
Purchase #3	$225.64	13.158%	$255.3297	$255.33	$255.35	$255.30
Purchase #4	$245.40	4.253%	$255.8369	$255.84	$255.85	$255.80
Purchase #5	$215.90	11.418%	$240.5515	$240.55	$240.55	$240.60
Purchase #6	$41.45	12.148%	$46.4853	$46.49	$46.50	$46.50
Purchase #7	$225.41	8.346%	$244.2227	$244.22	$244.20	$244.20
7 purchase totals =	$1,214.56		$1,314.1788	$1,314.18	$1,314.20	$1,314.20