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	$184.76	7.197%	$198.0572	$198.06	$198.05	$198.10
Purchase #2	$12.81	4.580%	$13.3967	$13.40	$13.40	$13.40
Purchase #3	$152.54	9.326%	$166.7659	$166.77	$166.75	$166.80
Purchase #4	$126.60	11.859%	$141.6135	$141.61	$141.60	$141.60
Purchase #5	$34.97	6.144%	$37.1186	$37.12	$37.10	$37.10
Purchase #6	$240.73	10.203%	$265.2917	$265.29	$265.30	$265.30
Purchase #7	$239.82	10.449%	$264.8788	$264.88	$264.90	$264.90
7 purchase totals =	$992.23		$1,087.1224	$1,087.13	$1,087.10	$1,087.20