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	$84.66	5.241%	$89.097	$89.10	$89.10	$89.10
Purchase #2	$57.81	12.137%	$64.8264	$64.83	$64.85	$64.80
Purchase #3	$250.54	9.118%	$273.3842	$273.38	$273.40	$273.40
Purchase #4	$144.97	10.821%	$160.6572	$160.66	$160.65	$160.70
Purchase #5	$93.63	3.280%	$96.7011	$96.70	$96.70	$96.70
Purchase #6	$85.88	3.418%	$88.8154	$88.82	$88.80	$88.80
Purchase #7	$222.53	11.820%	$248.833	$248.83	$248.85	$248.80
7 purchase totals =	$940.02		$1,022.3143	$1,022.32	$1,022.35	$1,022.30