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	$64.41	6.240%	$68.4292	$68.43	$68.45	$68.40
Purchase #2	$228.80	9.524%	$250.5909	$250.59	$250.60	$250.60
Purchase #3	$178.71	7.259%	$191.6826	$191.68	$191.70	$191.70
Purchase #4	$89.36	10.290%	$98.5551	$98.56	$98.55	$98.60
Purchase #5	$152.68	10.795%	$169.1618	$169.16	$169.15	$169.20
Purchase #6	$188.58	11.675%	$210.5967	$210.60	$210.60	$210.60
Purchase #7	$171.85	7.796%	$185.2474	$185.25	$185.25	$185.20
7 purchase totals =	$1,074.39		$1,174.2637	$1,174.27	$1,174.30	$1,174.30