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	$211.43	8.718%	$229.8625	$229.86	$229.85	$229.90
Purchase #2	$138.63	12.335%	$155.73	$155.73	$155.75	$155.70
Purchase #3	$245.71	7.196%	$263.3913	$263.39	$263.40	$263.40
Purchase #4	$144.56	12.279%	$162.3105	$162.31	$162.30	$162.30
Purchase #5	$104.72	8.321%	$113.4338	$113.43	$113.45	$113.40
Purchase #6	$50.73	5.539%	$53.5399	$53.54	$53.55	$53.50
Purchase #7	$170.46	12.192%	$191.2425	$191.24	$191.25	$191.20
7 purchase totals =	$1,066.24		$1,169.5105	$1,169.50	$1,169.55	$1,169.40