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	$53.79	9.834%	$59.0797	$59.08	$59.10	$59.10
Purchase #2	$53.43	11.531%	$59.591	$59.59	$59.60	$59.60
Purchase #3	$200.28	3.467%	$207.2237	$207.22	$207.20	$207.20
Purchase #4	$78.89	4.321%	$82.2988	$82.30	$82.30	$82.30
Purchase #5	$54.72	3.154%	$56.4459	$56.45	$56.45	$56.40
Purchase #6	$23.73	11.812%	$26.533	$26.53	$26.55	$26.50
Purchase #7	$42.76	8.275%	$46.2984	$46.30	$46.30	$46.30
7 purchase totals =	$507.60		$537.4705	$537.47	$537.50	$537.40