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	$121.28	4.543%	$126.7898	$126.79	$126.80	$126.80
Purchase #2	$55.95	8.839%	$60.8954	$60.90	$60.90	$60.90
Purchase #3	$242.71	10.186%	$267.4324	$267.43	$267.45	$267.40
Purchase #4	$82.97	8.282%	$89.8416	$89.84	$89.85	$89.80
Purchase #5	$158.27	8.711%	$172.0569	$172.06	$172.05	$172.10
Purchase #6	$172.69	11.212%	$192.052	$192.05	$192.05	$192.10
Purchase #7	$98.85	10.694%	$109.421	$109.42	$109.40	$109.40
7 purchase totals =	$932.72		$1,018.4891	$1,018.49	$1,018.50	$1,018.50