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	$174.31	12.797%	$196.6165	$196.62	$196.60	$196.60
Purchase #2	$211.86	8.279%	$229.3999	$229.40	$229.40	$229.40
Purchase #3	$233.41	3.200%	$240.8791	$240.88	$240.90	$240.90
Purchase #4	$89.45	13.205%	$101.2619	$101.26	$101.25	$101.30
Purchase #5	$72.87	12.292%	$81.8272	$81.83	$81.85	$81.80
Purchase #6	$59.55	7.696%	$64.133	$64.13	$64.15	$64.10
Purchase #7	$41.78	12.787%	$47.1224	$47.12	$47.10	$47.10
7 purchase totals =	$883.23		$961.2400	$961.24	$961.25	$961.20