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	$74.96	4.393%	$78.253	$78.25	$78.25	$78.30
Purchase #2	$93.40	9.688%	$102.4486	$102.45	$102.45	$102.40
Purchase #3	$99.85	6.333%	$106.1735	$106.17	$106.15	$106.20
Purchase #4	$240.67	4.164%	$250.6915	$250.69	$250.70	$250.70
Purchase #5	$81.72	5.399%	$86.1321	$86.13	$86.15	$86.10
Purchase #6	$185.45	10.195%	$204.3566	$204.36	$204.35	$204.40
Purchase #7	$236.32	8.437%	$256.2583	$256.26	$256.25	$256.30
7 purchase totals =	$1,012.37		$1,084.3136	$1,084.31	$1,084.30	$1,084.40