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	$176.51	4.218%	$183.9552	$183.96	$183.95	$184.00
Purchase #2	$99.55	5.829%	$105.3528	$105.35	$105.35	$105.40
Purchase #3	$204.48	3.292%	$211.2115	$211.21	$211.20	$211.20
Purchase #4	$65.61	11.612%	$73.2286	$73.23	$73.25	$73.20
Purchase #5	$103.96	5.120%	$109.2828	$109.28	$109.30	$109.30
Purchase #6	$150.94	9.672%	$165.5389	$165.54	$165.55	$165.50
Purchase #7	$55.66	6.712%	$59.3959	$59.40	$59.40	$59.40
7 purchase totals =	$856.71		$907.9657	$907.97	$908.00	$908.00