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	$61.39	11.686%	$68.564	$68.56	$68.55	$68.60
Purchase #2	$222.89	9.300%	$243.6188	$243.62	$243.60	$243.60
Purchase #3	$75.93	8.150%	$82.1183	$82.12	$82.10	$82.10
Purchase #4	$73.48	7.150%	$78.7338	$78.73	$78.75	$78.70
Purchase #5	$150.81	11.857%	$168.6915	$168.69	$168.70	$168.70
Purchase #6	$162.60	5.353%	$171.304	$171.30	$171.30	$171.30
Purchase #7	$221.48	8.415%	$240.1175	$240.12	$240.10	$240.10
7 purchase totals =	$968.58		$1,053.1479	$1,053.14	$1,053.10	$1,053.10