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	$98.45	4.855%	$103.2297	$103.23	$103.25	$103.20
Purchase #2	$250.87	7.461%	$269.5874	$269.59	$269.60	$269.60
Purchase #3	$56.70	6.445%	$60.3543	$60.35	$60.35	$60.40
Purchase #4	$54.91	11.312%	$61.1214	$61.12	$61.10	$61.10
Purchase #5	$179.30	8.275%	$194.1371	$194.14	$194.15	$194.10
Purchase #6	$120.82	4.495%	$126.2509	$126.25	$126.25	$126.30
Purchase #7	$187.59	9.653%	$205.6981	$205.70	$205.70	$205.70
7 purchase totals =	$948.64		$1,020.3789	$1,020.38	$1,020.40	$1,020.40